Sectored sensing band for dryers



p 1967* p D. E. JANKE ETAL 3,343,272

' SECTORED SENSING BANp FOR DRYERS Filed Nov. 17, 1964 3Sheets-Sheet 1 INVENTOR.

, s- I 88 u gfl/M M @4 4 v ATTORNEYS Sept. 26, 1967 D. E. JANKE ETAL SECTORED SENSING BAND FOR DRYERS Filed Nov. 17, 1964 5 Sheets-Sheet 2 'INVENTOR5 x04. 6/4/1465 6347/10/67 Qw ATTORNEYS p D. E- JANKE ETAL 3,343,272 3 SECTORED SENSING BAND FOR DRYERS} Fiied Nov. l' 7, 1964 5 Sheets-Sheet 5 QNN ATTORNEYS United States Patent 3,343,272 SECTORED SENSING BAND FOR DRYERS Donald E. Janke, Benton Harbor, and Sandy C. Gay, St.

Joseph, Mich., assignors to Whirlpool Corporation, Benton Harbor, Mich., a corporation of Delaware Filed Nov. 17, 1964, Ser. No. 411,799 3 Claims. (Cl. 3445) This invention relates generally to a clothes dryer having a device for sensing moisture content in the materials being dried and more particularly relates to sectored sensing bands which can be used in a receptacle or drum having integrally-formed bafiies, thereby completely eliminating the necessity of using individual insert baflies.

In accordance with this invention dryness sensing bands are sectored or divided into segments which are electrically connected externally of the drying receptacle to afford continued continuity around the inside periphery of the drum. The segments of the sensing band assembly can therefore extend between circumferentially spaced performed tumbling bafiies. Furthermore, the arcuate segments of the sensing band assembly are placed in a predetermined axial spaced relation inside the drying receptacle to provide continuous contact with a substantial portion of the material to be dried therein, thereby detecting the relative dryness of the material.

The illustrated embodiment of the invention is incorporated in a domestic clothes dryer but it will be understood that various principles and features of the invention can be applied to other types of material handling systems.

In the dryness control system of this invention, the dryness of clothes is measured electrically by measuring the electrical resistance presented between the segmented band assemblies engaged with spaced portions of a mass of clothes, the resistance being low when the clothes are wet and being increased as the clothes approach a dry state. The measured value of electrical resistance across the segmented bands may be indicated or may preferably be used to automatically control the operation of drive, air circulating and heating means incorporated in the dryer.

It is therefore an object of the present invention to provide in a drying receptacle, a dryness sensing assembly having a plurality of segments sized and shaped to accommodate a preformed tumbling baffle which is an integral part of the inner surface of the drying receptacle.

"fixed in position, with no edges or crevices or openings exposed to catch the clothes or lint or the like therein.

Many other objects, features and advantages of the invention will become more fully apparent from the following detailed description and the accompanying drawings.

On the drawings:

FIGURE 1 is a diagrammatic elevational view of the rear side of a dryer incorporating a dryness sensing band assembly and control system according to this invention;

FIGURE 2 is a front elevational view of a rotatable clothes receptacle shown in FIGURE 1 with parts broken away to show additional details of construction;

FIGURE 3 is a side elevational view of the clothes receptacle of FIGURE 2 with parts broken away to show additional details of construction;

FIGURE 4 is a side elevational view of one arcuate segment of a sensing band assembly used in the clothes dryer of FIGURE 1;

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FIGURE 5 is a sectional view taken substantially along line VV of FIGURE 4;

FIGURE 6 is an electricalcircuit diagram of a dryness sensing control system which is connected to the arcuate portions of the sensing band assembly of FIGURES 2 and 3; and

FIGURE 7 is a fragmentary plan view of one end of one of the sensing band assemblies of our invention.

As shown on the drawings:

A clothes dryer shown generally at 10 incorporates sensing segments to form a sensing band assembly in accordance with the present invention, whereby the dryness of clothes is sensed by electrical resistance measurement to automatically control the de-energization of drive and heating means while affording a particularly efi'icient form of bafiling as provided by an internally ribbed drum.

In the illustrated dryer 10, clothes to be dried are placed within a drum 12 disposed within a casing 14. The drum 12 is journalled for rotation in a bearing assembly 16 about a horizontal axis. To drive the drum 12 and tumble the clothes therewithin a belt 18 is trained about the periphery of the drum and about a pulley 20 driven by an electric motor 22. For drying the clothes, air enters from the lower portion of the casing 14 through an inlet opening 24 in a back panel 26 of the casing 14, into a duct 28 having an electric heater 30 therewithin. Heated air from the duct 28 passes through an outlet opening 32 and into the drum 12, through openings in the back wall thereof. The air, after picking up moisture from clothes within the drum, is withdrawn from the drum into the inlet 34 of a blower 36 which discharges from the blower through a vent 38 in a partial back panel 40 and through a suitable pipe (not shown) to the outside atmosphere. The blower 36 is driven -by -a pulley 42 which, in turn, is driven by a belt 44 from a pulley 46 mounted on the shaft of the motor 22.

The motor 22 and heater 30 are connected to a control circuit 48 through cables 50 and 52, the control unit 48 being connected through a wire 54 to the dryness sensing assembly of the present invention.

As shown in FIGURE 2, the drum 12 is particularly characterized by an inner wall member 56 which has integrally preformed thereon tumbling baflles 58, 60 and 62. The baflles 58, 60 and 62 are herein shown as integral radially inwardly extending em-bossments spaced at equal distances from one another along the circumference of the drum wall 56. Each baffle has a leading edge 58a, 60a, and 62a disposed at a, more pronounced angle than is the tracking edge shown at 58b, 60b and 62b. The baffles 58, 60 and 62 extend transversely across the cen tral portion of drum 12, the opposite ends of each baifie tapering outwardly to join the lateral edges of the peripheral drum wall 56, as shown at 620 in FIGURE 3. Thus, the drum surface is provided with alternately circumferentially spaced ribs and wall areas which promote a good tumbling action for a batch of clothes in the drum as the drum is rotated at tumbling speeds.

A front wall member 64 is secured to the wall member 56 in such a manner as to provide a leakproof joint about the peripheral edge 66 of the drum 12. An opening 68 is provided in the front wall member 64 for receiving clothes to be dried in the drum 12.

The rear wall member of the drum 12 is shown at 70 and has a centrally embossed portion 71 forming a recessed area. A bearing wall 72 extends across the recess and carries a bearing 74 by means of which the drum 12 may be supported for rotation. The bearing 74 also provides electrical contact to ground potential for the electrical sensing control of the invention.

In accordance with the invention there is secured to the inner wall portion of the drum 12 a plurality of arcuate sensing segments 76, 78 and 80 between the ribs or baffles 58, 60 and 62. As shown in FIGURE 5, each arcuate segment 80 comprises two metallic arcuate strips 82 and 84 which are secured to a molded insulating segment 86.

As shown in detail in FIGURES 4 and 5, the metallic sensing strips 82 and 84 are secured to the molded insulating segment 86 in such manner as to provide a grounded condition for the sensing strip 84 and an insulated condition for the sensing strip 82, thereby allowing a voltage to be sensed between the sensing strips 82 and 84. By way of example, the arcuate sensing segment 80 comprises an insulating segment 86 which is molded of polypropylene. The insulating segment 86 has formed therein a pair of channels 87 and 89 for receiving arcuate sensing elements 82 and 84, made of electrically conductive material such as stainless steel.

Formed at each end of channel 87 is an opening 106 arranged to receive a fastener 88a therethrough for securing the sensing element 82 in the channel 87. Formed at each end of the channel 89 is an opening 105 arranged to receive a fastener such as a screw 88 therethrough for securing the sensing element 84 in the channel 89. The fasteners 88 and 88a at each end of the arcuate sensing segments also serve to secure the sensing segments 80 to the inner wall 56 of the drum 12. Located intermediate the channels 87 and 89 and coextensive therewith is a structural protuberance or rib 91w extending radially inwardly further than the sensing elements 82 and 84. The head portion 90 of each screw 88 is received in a hollow area 92 formed in the metallic sensing element 84 by a curved body portion 94 and a pair of inwardly extending legs 96. Similarly, the fastener 88a is received in metallic sensing strip 82.

At each end of the channels 87 and 89 are cap portions 91 molded as an integral part of the insulating segment 86. The cap portions 91 are located to receive the end portions of the arcuate sensing elements 82 and 84 to provide means for securing the ends of the sensing elements 82 and 84 to the insulating segment 86 and to also provide a smooth cover for the edges of the ends of the sensing elements 82 and 84.

The insulating segment 86 is preferably molded in a flat plane configuration rather than in the arcuate shape shown in use to facilitate the molding operation. The metallic sensing elements 82 and 84 are formed to the arcuate shape in which they will be assembled. To assemble the arcuate sensing segment 80 as shown in FIGURE 4, the head portions of the fasteners 88 and 88a are positioned into the hollow areas 92 of the sensing elements 82 and 84 respectively. The semi-flexible, resilient polypropylene insulating segment 86 is forced into the arcuate configuration of the sensing elements 82 and 84 and the fasteners 88a and 88 are inserted through the respective openings 106 and 105 in the insulating segment 86. The sensing elements 82 and 84 are located in channels 87 and 89 respectively. The ends of the sensing elements 82 and 84 are assembled into the cap portions 91 by bending the ends of the arcuate insulating segment 86 about a transverse axis illustrated by point 93 in the direction opposite to that of the curvature of elements 82 and 84 to open the cap portion 91 to permit the insertiOn of the ends of the sensing elements 82 and 84 into segment 86. After the entrance of the ends of the sensing elements 82 and 84 into the cap portions 91, the ends of the insulating segment 86 are released to resume the desired arcuate shape to provide securing means to hold the sensing elements 82 and 84 in assembly with the insulating segment 86.

As shown in FIGURE 5, the screw 88, which is secured to the arcuate sensing strip 84, passes through an opening 100 in the wall member 56. A lock washer 102 and a nut 104 are received on the threaded portion of the screw 88. Each lock washer 102 is of conventional form being made of a conductive material and shaped with a sharp edge which cuts through any insulative coating which may be on the adjoining surface of the drum 12, thereby insuring good electrical contact, while also preventing loosening of the threaded connection which might otherwise be caused by vibration.

The screw 88a passed through an opening 106 which has formed therearound an insulating flange 108 which, in turn, passes through an opening 110 in the wall member 56 of the drum 12. An insulating washer 112 is placed over the threaded portion of screw 88a and circumscribes the insulating flange 108, while a second insulating washer 114 is placed over the threaded portion of screw 88a and overlies the insulating washer 112, thereby maintaining an electrically insulated relationship.

A terminal 116 is connected between the conductive nuts 118 and 120 to establish an electrical contact with the arcuate sensing strip 82, which is placed at a potential above ground potential for sensing the relative dryness of clothes. Connected to the terminal 116 is a conductor 122 which is adapted to be connected to a dryness sensing control circuit.

The arcuate segments 76 and 78 are constructed and fastened to the wall member 56 of the drum 12 in substantially the same manner as arcuate segments 80. In order to promote circumferential continuity of the segmented sensing bands, the corresponding segments are connected in series. Thus, sensing strips 82 of each of the arcuate segments 76, 78 and 80 are electrically connected together by a pair of conductors 124 and 126, while the sensing strips 84 of the arcuate segments 76, 78 and 80 are electrically connected together and to ground potential through the lock washer 102 and the nut 104.

To provide electrical contact of a high potential to a portion of the sensing band assembly, the conductor 122 is connected to a slip ring 128 which is carried by an insulating band 130 and circumscribes the peripheral surface of the drum 12 as shown at 132. A brush member B provides electrical sliding contact with the slip ring 128 for applying high potential thereto and subsequently to the sensing strips 82 of the arcuate segments 76, 78 and 80. The circumferential proportion of the segments considerably exceeds that of the ribs or baffies, thus establishing circumferentially spaced sensing areas to be bridged by the clothes. In tumbling a typical batch of clothes therefore, the clothes will be present in one or another of the sensing areas for developing the control functions of the invention. The battles, of course, assist in moving the clothes into such areas.

Referring now to the electrical circuit diagram of FIG- URE 6, the motor 22 has a main winding 200 and a starting winding 202 initially connected in parallel through a contact 204 of a centrifugal switch 206. The contact 204 is disconnected from the centrifugal switch 206 and the switch 206 is connected to a contact 208 when the motor reaches a certain speed.

The common connection of the windings 200 and 202 are connected to a neutral line 210, while the independent connection of the main winding is connected through a conductor 212 and through a normally open contact 214 of a relay 216 to a circuit point 218 which is connected through a door switch 220 to a line L1. The door switch 220 is physically located in such relation with the drum access door so as to be actuated to the closed position upon closing of the door and thereby completing the electrical connection to the control circuit, and deenergizing the electrical control circuit and the drive motor and heater when the door is open.

One terminal of an operating coil 222 of the relay 216 is connected to a push-to-start switch 224 through a diode 226. The push-to-start switch 224 is a normally open spring-biased switch which is momentarily manually actuated to initiate a cycle of operation of the clothes dryer 10. The other terminal of the coil 222 is connected to the anode of a silicon controlled rectifier 228 having a cathode connected through a resistor 230 to ground and also connected through a conductor 232 to the neutral line 210.

The silicon controlled rectifier 228 has a gate voltage applied thereto through a shunting circuit which comprises a resistor 234. To render the silicon controlled rectifier 228 conductive, a current will pass from the cathode electrode and therefrom to the gate electrode through the shunting resistor 234, thereby creating the necessary firing current through the gate-to-cathode junction and thereafter allowing the main current to pass through the ca-thode-to-anode junction for energizing the relay coil 222.

Afterthe relay coil 222 is thus energized to close the contact 214 and start the motor 22, a holding contact arm 236 is actuated and engaged with a fixed contact 238 to short circuit the start switch 224, and thereafter automatically apply power to the entire sensing control circuit. Also, a contact 240 is actuated by the relay coil 222, thereby applying power from the lines L1 and L2 to a resistance heating element 242.

The silicon controlled rectifier 228 is controlled in response to dryness, which is sensed as an increasing resistance between the line 244 and ground 246 by the dryness sensing assembly 248, and thereby renders the silicon controlled rectifier 228 nonconductive when the sensed resistance reaches a predetermined value.

More specifically, the cathode terminal of the diode 226 is connected through a diode 250, a resistor 252 and an adjustable resistor 254 to a circuit point 256-. The circuit point 256 is connected to a circuit point 258 which, in turn, is connected through a resistor 260 and a capacitor 262 to the cathode of the silicon controlled rectifier 228. Also, the circuit point 258 is connected through a resistor 264 and a neon lamp 266 to the base electrode of a transistor 268. The emitter electrode of transistor 268 is connected to the gate electrode of silicon controlled rectifier 228, while the collector electrode of transistor 268 is connected to the cathode electrode of silicon controlled rectifier 228.

In operation, the capacitor 262 is charged by current flow through the circuit including the resistors 252 and 260, the variable resistor 254 and the diode 250. Initially, when the clothes are wet, the amount of charge upon the capacitor 262 is limited by the resistance sensed by the dryness sensing assembly 248 which shunts the capacitor 262. The variable resistor 254 can be adjusted to provide a limited amount of control for selecting the desired dryness of clothes.

As the clothes, which are in contact with the dryness sensing assembly 248 are dried, the resistance of the shunt circuit increases and ultimately the charge across capacitor 262 increases to a level such as to cause the neon lamp 266 to discharge through the base emitter circuit of transistor 268. The transistor 268 then conducts thereby shunting the firing current between the cathode and gate electrodes of the silicon controlled rectifier 228 to render it nonconductive during the next half cycle of voltage applied thereto. The diode 226 in circuit with the relay holding coil 222 blocks the negative half cycles of voltage from the line L1. The silicon controlled rectifier 228 will remain nonconductive for as long as the neon lamp 226 is ionized, which by way of example, is approximately /a second in the present invention.

Upon rendering the silicon controlled rectifier 228 nonconductive, the relay coil 222 is de-ener-gized to open the contacts 214, 236 and 240. The electric heating element 242 is then de-energized; however, energization of the motor 22 may be continued through a cool-down thermostat 270 connected between the contact 208 of the motor cetnrifugal switch and the line L1.

The thermostat 270 is mounted in the blower 36, FIG- URE 1, and protrudes through a circular opening in the blower wall in order to sense the temperature of the exhaust air flowing through the blower. The thermostat includes a switch which is closed when the dryer is heated in the drying drum is reduced.

The resistors 252 and 254 should preferably have a relatively high resistance to provide a delayed action between the attainment of a certain dryness level and the de-energization of the heater. This delayed action allows the clothes to become quite dry, without imposing critical adjustment requirements on the resistance measuring cirsuit, which might otherwise create a critical shut-off condition. By way of example, the variable resistor 254 may have a selective value between .47 and 22 megohms, the resistor 252 has a value of 6800 ohms, the resistor 260 has a value of 22,000 ohms, the resistor 264 has a value of 10,000 ohms and the resistor 234 has a value of 8200 ohms.

The resistor 230 is provided as .a safety precaution in the event line L1 and line 210 are reversed when being connected to the usual source of electrical power and the neutral line 210 is connected inadvertently to the casing of the dryer 10. Thus, the resistor 230 may preferably have a value of l megohm. The capacitor 262 may have a value of 4 microfar-ads. Upon de-energization of the relay coil 222, the contract arm 236 moves to engage a contact 272 and thereby provides a discharge path for the capacitor 262 through the resistor 260, the resistor 274, the diode 226, the solenoid coil 222, the resistor 234 and the gate-to-cathode junction of the silicon controlled rectifier 228. The complete discharge of the capacitor 262 conditions it for a subsequent drying operation and also eliminates the possibility of a shock hazard to the operator who may accidentally or intentionally contact the sensing bands 82 inside the drum 12.

It will be apparent that other resistance measuring circuits may be employed and also that the circuit might be used to control heating means other than the electrical heating means as illustrated, such as for example, gas fired heaters where the ignition and supply of gas may be electrically controlled.

It should be understood that we wish to embody with in the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of our contribution to the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a clothes dryer for drying fabrics,

sensing means for a-dryness sensing system comprising a plurality of sensing segments each including an arcuate member made of electrically insulating material and curved to conformably engage the inside surface of a dryer drum wall,

each of said sensing segments having a pair of longitudinally extending channels formed therein, each of said arcuate members includes a radially inwardly extending rib disposed between said channels and being longitudinally coextensive therewith,

a sensing band in each channel comprising a strip of electrically conductive material having a radially inwardly projecting portion extending out of each corresponding channel for contacting fabrics to be dried,

and circuit means connected to said sensing bands to control the operation of the dryer as a function of the dryness of said fabrics.

2. In a dryer,

a drum having an outer curved peripheral Wall,

a plurality of circumferentially and alternately spaced baifies and sensing areas on said wall,

spaced openings in said wall,

a sensing segment in each sensing area comprising an arcuately-shaped insulating member made of electrically nonconductive material and having an outer surface conforming to the curvature of said peripheral wall,

said insulating member having an inner surface and provided with a pair of spaced circumferentially extending channels formed therein and a radially inwardly extending rib disposed between said channels and being longitudinally coextensive therewith,

said channels having openings formed at opposite ends thereof to register with said spaced openings formed in said drum wall,

the openings in one of said channels having insulating flanges projecting through said drum wall,

fastener means extending through said openings and a sensing strip made of electrically conductive material positioned in each channel and retained by said fastener means,

whereby said sensing strips may be connected to an electrical control circuit for regulating dryer operations as a function of dryness of materials placed within said drum.

3. In a dryer as defined in claim 2,

said fastener means including a plurality of headed bolts having heads positioned in corresponding ones of said channels and shanks extending through said openings,

and said sensing strips including curved portions receiving and concealing said heads and presenting smooth curved sensing surfaces to the interior of the drum for contacting said fabrics.

References Cited UNITED STATES PATENTS 2,332,846 10/1943 Fladd 174-1384 2,991,641 7/1961 Woodling 34-45 X 3,122,426 2/ 1964 Horecky 34-45 3,186,105 6/1965 Nye et al. 34-45 3,197,885 8/1965 Smith 34-45 3,210,863 10/1965 Nye et al, 34--45 3,250,018 5/1966 Edwards 34-45 FOREIGN PATENTS 571,724 10/ 1958 Belgium. 1,127,175 8/1956 France.

FREDERICK L. MATTESON, JR., Primary Examiner.

JOHN J. CAMBY, Examiner. 

1. IN A CLOTHES DRYER FOR DRYING FABRICS, SENSING MEANS FOR A DRYNESS SENSING SYSTEM COMPRISING A PLURALITY OF SENSING SEGMENTS EACH INCLUDING AN ARCUATE MEMBER MADE OF ELECTRICALLY INSULATING MATERIAL AND CURVED TO CONFORMABLY ENGAGE THE INSIDE SURFACE OF A DRYER DRUM WALL, EACH OF SAID SENSING SEGMENTS HAVING A PAIR OF LONGITUDINALLY EXTENDING CHANNELS FORMED THEREIN, EACH OF SAID ARCUATE MEMBERS INCLUDES A RADIALLY INWARDLY EXTENDING RIB DISPOSED BETWEEN SAID CHANNELS AND BEING LONGITUDINALLY COEXTENSIVE THEREWITH, A SENSING BAND IN EACH CHANNEL COMPRISING A STRIP OF ELECTRICALLY CONDUCTIVE MATERIAL HAVING A RADIALLY INWARDLY PROJECTING PORTION EXTENDING OUT OF EACH CORRESPONDING CHANNEL FOR CONTACTING FABRICS TO BE DRIED, AND CIRCUIT MEANS CONNECTED TO SAID SENSING BANDS TO CONTROL THE OPERATION OF THE DRYER AS A FUNCTION OF THE DRYNESS OF SAID FABRICS. 